1. Field of the Invention
The present invention relates to a laminated electrically conductive sheet, a producing method thereof, a current collector, and a bipolar battery, to be specific, to a bipolar battery preferably used for a lithium ion secondary battery, a current collector provided therein, a laminated electrically conductive sheet, and a producing method thereof.
2. Description of Related Art
In view of requiring high energy density and high output density for an electric vehicle (EV) and a hybrid electric vehicle (HEV), a lithium ion secondary battery is mounted thereon.
In the lithium ion secondary battery, in order to achieve further higher energy density and further higher output density, a bipolar battery in which a cathode active material and an anode active material are disposed at both sides of each of a plurality of current collectors has been considered.
In recent years, in order to achieve weight reduction of the bipolar battery and to improve the output density per unit mass, for example, a bipolar battery consisting of a plurality of electrodes, each of which is provided with a current collector made of a high polymer material, a cathode electrically bonded to one surface of the current collector, and an anode electrically bonded to the other surface of the current collector, and electrolyte layers, which are disposed between a plurality of the electrodes, has been proposed (ref: for example, Japanese Unexamined Patent Publication No. 2006-190649).
In the bipolar battery proposed in Japanese Unexamined Patent Publication No. 2006-190649, however, the current collector made of a high polymer material has lower barrier properties of an electrolytic solution than that made of a metal foil, so that there is a disadvantage that lithium ions permeates the current collector in the laminating direction and liquid junction occurs between the cathode and the anode.
In order to solve such a disadvantage, a current collector for a bipolar battery including a resin layer, which has electrically conductive properties, and at least one-layered ion-blocking layer, which has electrically conductive properties and suppresses permeation of ions in a direction perpendicular to a surface, has been proposed (ref: for example, Japanese Unexamined Patent Publication No. 2010-277862).
In Japanese Unexamined Patent Publication No. 2010-277862, as a method for fabricating a current collector for a bipolar battery, a method in which a resin layer and an ion-blocking layer made of a metal foil are attached to each other by thermal compression bonding or a method in which an ion-blocking layer made of a metal is formed on a resin layer by sputtering is proposed.